Summer 2023 in the non-tropical Northern Hemisphere was the hottest in 2,000 years.

• Surface air temperatures were more than 2°C higher than the average summer temperature between 1 AD and 1890.

• The warming is linked to greenhouse gas emissions and amplified by El Niño.

• Tree ring data was used to reconstruct past summer temperatures.

• Climate change is causing more frequent and severe heatwaves.

• Rising temperatures are stressing trees and leading to forest die-offs.

Read more at The Conversation website.